


Our Secret

by SpyroForLife



Category: Gravity Falls
Genre: Casual Sex, Drabble, F/M, NSFW, One-Shot, Polyamory, Smut, this isn't a threesome though
Language: English
Status: Completed
Published: 2015-06-25
Updated: 2015-06-25
Packaged: 2018-04-06 01:18:30
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,123
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4202445
Author URL: https://archiveofourown.org/users/SpyroForLife/pseuds/SpyroForLife
Summary: <blockquote class="userstuff">
              <p>Bill Cipher gives Mabel a visit one afternoon to speak with her about certain fantasies he has seen in her dreams. He may be in a relationship with Dipper, but he wouldn't mind indulging Mabel just this one time...</p>
            </blockquote>





	Our Secret

**Author's Note:**

> I really have no excuse I just wanted to write Mabel/Bill. The attraction is only sexual, however; Mabel is perfectly content for Bill to remain in a relationship with Dipper, but she isn't going to refuse sleeping with him if he offers. It'll be their little secret~  
> This has no relationship to anything else I've written but I just wanted to share it. Enjoy? D:

A series of taps on the door made Mabel look up from the new sweater she was knitting. That clearly wasn't her brother; he always used their signature knock. “Yes?” she called.

“May I come in?” a familiar, polite voice said.

“Sure.” Mabel put on a smile as the door opened and Bill stepped into the room. He was beaming as always, his ever-present cheerfulness sending flutters right through her. It seemed his human body became more handsome every time she saw it, too. Yet again, she felt jealousy that her brother had claimed him first. He may be a demon, but he was _dazzling_.

“How are you, Shooting Star?” Bill asked, giving her a charming grin.

“Good. Just making a new sweater. It'll be winter soon.” She held it up to show him her progress. “I just started, but it's purple, and I'm gonna put snowflakes on it, I think. Or mugs of hot chocolate. Or maybe more little sweaters! What do you think?”

“Hmm...” He walked over to the bed, leaning down to examine it, which also put him very, delightfully close to her. “Maybe candy canes and marshmallows and other yummy things?”

“Ooh, yeah! Good idea. So, what's up?”

Bill sat next to her, lounging back a little. “Nothing much. Pine Tree had to go to the electronics store to buy a new charging cable for his laptop because I totally didn't destroy the other one in a science experiment.”

“Oh man, he'll be gone for a while, then. He's picky.”

“Exactly. He just left, so I figured I'd hang out with you.”

“Well, I was mostly just gonna knit...”

“You can do that, but I want to talk about something.”

Something about his tone made Mabel nervous. “Oh. Uh... what?”

He was looking directly at her, his grin becoming more of a strangely smug smirk. “You've no doubt grown used to seeing me like this. But don't forget, I  _am_ a dream demon. When this body sleeps, I roam the mindscape in my normal form, just like I've been doing for eons. Usually I just hang out with Pine Tree in his dreams, but I check out other dreams. The neighbors. The mayor. Your parents. You.”

She felt a sinking sensation. “Oh. So you've seen my dreams?”

“Yeah. Most are what I would expect. Colorful, happy, trippy. I was fairly entertained on my first few trips into your mind. But one night...” He chuckled, and she found herself blushing, fearing the worst. “You are really interested in my human body, aren't you?”

“Oh, well, um...” She fiddled with her needles. “You're... cute. Like... really cute... oh my gosh you're so pretty! I'm sorry, I know you're with Dipper, I just... like to pretend, sometimes.”

“Why pretend?” Bill removed the needles from her hand, setting them and her partly-finished sweater aside on a table. Then he returned his hands to hers, winding their fingers together.

“Bill, no, what are you doing?” She tugged her hands away.

“Making your dreams come true, Shooting Star,” he purred.

“I like you, but I don't want you to cheat on Dipper with me!”

“Dipper is... open-minded,” Bill replied smoothly. “There's plenty of me to go around. Come on, it'll be fun.”

“Just because it's fun, it doesn't mean it's right.”

“Shoot- Mabel. Mabel, come on.” He took her hands again, and this time, she didn't pull away. He grinned at her, and her stomach did a somersault. “Just for fun. Just some casual stuff. It doesn't have to mean anything.” His voice was like honey. “Let's have some fun, star. It will all be fine.”

She was hesitant, but Bill was handsome and attractive and  _willing_ and maybe she should just go with it...

Then he leaned forward and kissed her. With complete confidence and no inhibitions, he kissed her on the lips. Her eyes widened, but she knew a thing or two about kissing, and he was  _good_ . But considering how much lip-locking he did with Dipper, that made sense.

She sighed and responded, trying her best to keep up with his experienced lips. His hands left hers and instead grasped her cheeks, and she realized he was actually tilting her head so it was more comfortable for him. The aggression made her heart pound. She had figured he was dominant, but didn't think it was to this degree.

There was suddenly pressure on her lap, and she squeaked in surprise as he straddled her, legs on either side of her and chest pressed to hers as he deepened the kiss.

She felt lightheaded when his tongue slid along hers, and she almost panted as she felt just how warm and dry his mouth was. Her eyes fell shut and she leaned toward him, hands finding home on his bony hips, which she could feel easily through his dress pants.

Bill separated and looked thoughtfully at the flustered young woman. “Hmm... You seem enthusiastic.”

She opened her eyes, looking away and huffing. She brushed some hair back behind her ears. “A hot guy is sitting on my lap kissing me. It's natural to be enthusiastic.”

“You would think that but you'd be surprised how often I got slapped in bars.”

“But... I just don't feel right, you're Dipper's boyfriend...”

“Don't worry about Dipper. I'll deal with him later. I want to do this with you. I don't get why you humans get so focused on just one person at a time. Where's the adventure in that? I want to experiment. I want to play with whoever I can.”

“I... guess that makes sense, just... people are kinda greedy. They like having an intimate relationship with someone that no one else can get involved with. It makes it more special. But... if you're okay with it...”

“Mmhmm...” He kissed her again, more tenderly. “It's all fine. If Dipper gets angry, I'll deal with it. I won't let him blame you. I'll tell him I brainwashed you or something.”

“Can you do that?”

“If I wanted. But that takes all the challenge out of the art of seduction, which I am currently perfecting.” He began necking her, and she shuddered as he breathed hotly against her throat. “Let's see if this works on you like it does on your brother...” He nipped at the skin, giving a little twist, and she jumped.

“Don't bite me!” she admonished. In response to his startled look, she said, “I'm not into biting. Or scratching, really.”

“Oh. Okay, I can work with that.” He licked instead, enticing a moan out of her. Then he suckled over her pulse, and she squirmed, fingers clenching harder into his hips.

“I do like that,” she whispered, eyes losing focus as she relaxed in his hold.

“Good. What else do you like?” Bill sat up more, brushing his nose through her hair. It smelled like her vanilla shampoo, and he didn't care much for the sense of smell, but it was kinda nice. And she seemed to enjoy it, which was the point.

“Mmm... lots of snuggling throughout, and stroking... Just don't do that masochist stuff. That's Dipper's thing.”

“Got it. So, you're into affectionate stuff?”

“Yeah.”

“Hmm. So, slow and tender sex is probably your thing.” He grinned when her face grew red. “Right? And don't tell me you wouldn't know, because you know.”

She nodded, embarrassed. She hasn't been a virgin since she was sixteen. It wasn't that big a deal to her, she was just still kinda upset that the guy hadn't been 'the one.' She's messed around with various boys since, but it was never anything serious. She was quite lighthearted about it by now and didn't usually mind casual sex. But considering that Bill was with someone...

“Cool, I can do that.”

“Can you, Mr. Tough Guy? I've seen the bruises that you leave on Dipper. Do you even know the meaning of the word 'tender'?”

Bill's golden irises gleamed. “Let me show you.” He pushed her down onto her back under him and rested his weight on her, kissing her sweetly. She was startled, but responded to him. As they kissed, she moved her arms up to wrap around his middle. Okay, who cares if he has a boyfriend? He was eager and she wanted him and whatever happens, happens.

A warm hand suddenly touched her side, and she realized he was reaching under her sweater. Before she could decide how she really felt about that, he pulled his face back and said, “With your permission, Shooting Star.”

She stared at him for a good minute. It was unusual for a man to actually ask her. She would have been okay with it anyway, but she really appreciated his respect. “Yeah. Go for it.”

“With pleasure.” He slid his hand up further, cupping one of her breasts through her bra. She sighed softly, and shifted when he squeezed lightly. He kissed her again, and stroked a little underneath the fabric.

After a few minutes, he managed to get her sweater off, and then tugged off her shirt.

Giving her a few moments to collect herself, he sat back on her hips so she could watch him undress. He wasn't wearing his favorite tailcoat, bowtie, or shoes at the moment, since he's been inside all day today. He just had on dress pants and a white collared shirt. He slowly unbuttoned the shirt, and saw her eyes widen, never leaving his chest. He pulled the shirt open, untucking it from his trousers as he did. She swallowed as she saw his toned abdomen.

“Doing okay?” he asked.

She nodded.

“Still wanna do this?”

“Yeah. It'll be fun.”

“That's the spirit!” He pulled his arms out of the sleeves and tossed the shirt aside, and began unzipping his pants.

Mabel's fingers clenched into the covers under her, and she could feel her heart pounding hard in her chest. She hasn't felt this anxious about sex since her first time. But Bill was unpredictable and had the potential for violence, so it was justified, in her opinion.

Yet his hands were gentle as he reached back down and petted her shoulders, and ran his fingers through her hair. They were small actions, but they helped her relax. When he stroked her cheek, she closed her eyes and smiled. So Bill  _could_ be tender! Dipper was so lucky...

She felt his lips press to hers briefly, and his hands left her face, moving down. She didn't think too much of it until she felt a hand on the inside of her thigh, dipping underneath her skirt. He rubbed in small circles against her skin, and she felt a heat travel through her body. A groan escaped her, encouraging him.

“Can I remove this?” he asked sweetly.

She couldn't believe that Bill, an antagonistic dream demon with boundless arrogance, could be so considerate. She's been with decent guys that would get to this point and then demand she 'take that off' or just remove the article of clothing themselves without asking. So she was pleasantly surprised by how Bill was treating her.

Then again, demons were pretty big on consent. Sure, they'll take your soul, but they'll make sure you agree to it first.

“Go ahead,” she answered.

His slender fingers traced over her legs, then he grasped the skirt and tugged it down. He put it aside and stroked her sides and belly, making her giggle.

“Hey,” she said playfully, “Why am I the only one in my underwear? Take your pants off.”

He chuckled. “Sure.” He first reached into a pocket and removed something, but it was easily hidden in his fist so she couldn't tell what it was. Then he pulled his pants down and shifted to take them off, throwing them in the general direction of his shirt.

“That's better.” She admired him for a few moments. It was obvious he exercised. Then she pulled him down on top of her for a kiss. He responded with enthusiasm, and she felt warmth pool in her at the bare, skin to skin contact. His hand moved under her back, fingers working at the clasp in her bra. In seconds, he had unhooked it and pulled it off. She moved her arms to get the straps off, and he tossed the garment aside.

He was straddling her again, and as they kissed, he slowly ground his hips against hers. A little shiver passed through her body as she felt his erection through the fabric of their underwear. And as he rubbed against her, she could feel him grow harder.

After a few moments, Bill pulled back and looked down at her, smiling and brushing her hair out of her face. “Ready to keep going?” He held up his hand and opened it, showing her a condom packet.

And he used protection. Mabel was pretty much sold. “Yes!”

“All right. Liking the positive attitude.” Bill sat back on his heels, removing his underwear. “I'll put this on and you can do something with those panties, hmm?”

About a second later, she was twirling them around a finger. “How's this?”

“That works.” He laughed as he carefully rolled the condom over his length. “I'll be honest, I've never used one of these before. There's no need to with Dipper because neither of us have diseases and also can't get pregnant. But you seem to have a uterus and therefore likely have fertile eggs, so I don't wanna get you pregnant. Cool?”

“Cool.” Mabel stretched back the underwear like a rubber band and shot them off in a random direction before devoting her full attention on Bill.

“Awesome. Okay, let's see...” Bill reached down between her legs and gave her a curious stroke. She bit her lip, almost glancing down, but keeping her eyes on his. He was smiling as usual, looking pleased with himself for getting to this point. And when he found where she was most sensitive and she moaned, his face lit up with excitement. “Ah, there! Okay, that's not difficult. Bear with me, I need to relearn some things.”

He spent a few minutes just touching her, and her thighs were soon quivering, sweat breaking out on her skin. She felt much too warm, and things were just getting started. On top of that, she was aware of wetness between her legs and a light pulsing sensation.

“Bill, geeze...” she groaned, starting to feel frustrated. “Can you hurry up?”

“Certainly. What do you want me to do?”

“I want you to... I don't know, go down on me or something.” She said it mostly out of annoyance, and immediately felt bad and started to apologize for being so brash. But Bill did exactly that, and she tossed her head back and cried out in pleasure as his tongue dove inside her, lips moving in a way that just made her want to scream. She managed to stifle that, though; her parents weren't home, but she was used to keeping it quiet.

Bill, however, was just as aware that they were alone. He looked up at her and paused so he could grin, tongue still sticking out a little. “No, go ahead and make all the noise you want. I'm really into that. I've gotten good at figuring out what you guys want just from the sounds you make.”

“Well, if you- oh God!” She yelled as he returned to his task, fingers grasping his hair and pulling on it slightly. He didn't stop, though he did reach up to press a hand to her forehead, and she heard his voice in her mind.

'Please don't pull on my hair. I don't like that.'

“I thought you were into pain, Bill,” she teased. She could feel him snort.

'That's not painful, it's just annoying.'

“Oh, sorry. How about this?” She settled for affectionately stroking his hair, massaging the back of his head and behind his ears a little, and he smiled.

'That's nice. Wow, scratch behind my ear again... holy shit, that's awesome. Gonna have to tell Pine Tree about that one.' He removed his hand and lifted his head, licking his lips off. “How was that?”

She was breathless. “It was great. Have you done that before?”

“Not quite. But it wasn't hard to figure out what to do. Heh, this is so interesting. You ready for the main event?”

“More than I'll ever be,” she replied.

“All right. If you feel uncomfortable at any point, let me know.”

“You know, I never thought you would be this polite. It's so weird, are you like this with Dipper?”

“Sometimes. Though he and I share a deeper connection than I do with you. It's almost as if I can read his mind without even touching him. I can hold him and just feel what he wants me to do, so we don't communicate this much. And I've learned what he's into and what he isn't. But I don't know with you. I have to learn where your limits are. So I gotta talk to you.”

“Oh. I guess that makes sense. Just... you always seem so aggressive with Dipper, I figured you would be like that in bed too.”

“Do you want me to be like that?”

“Uh...” She drew back slightly at the predatory look he gave her. “Maybe not. I prefer it gentle...”

“Okay then. Lay back and get comfortable.” Bill put a hand on her shoulder, but didn't push. He waited for her to lay down on her own, and then slid his hand down the length of her body, putting a little bit of pressure on her. It was surprisingly sensual, and she felt some of her tense muscles relax. She looked up at the demon, at his large, intelligent eyes filled with amusement, the sharp lines of his face, his blonde hair that was probably softer than hers because he was completely obsessed with beauty products. Really, he wasn't the worst supernatural creature she could find herself in bed with.

He set a hand on the bed to provide some support, and settled the other on her hip, thumb stroking the curve of the bone. Then he shifted her lower body so her legs were on either side of him, and pressed against her entrance. She grabbed his upper arms, not to stop him, but simply because she knew she would need something to hold on to.

Before she really had time to consider that she was actually doing this, he was inside her, and she was crying out his name. He moved easily, fluidly, making her entire body rock in time to his rhythm. Pretty soon, she had her arms wrapped around his torso and her face buried against his chest, moaning and moving the best she could back against him.

“Mm, Shooting Star...” Bill murmured against her ear, making electricity tingle down her spine. “Are you enjoying yourself?”

“Yes,” she gasped, opening her eyes briefly and leaning back to look at him. His expression was devious, a small smirk on his lips, and she could only wonder what he thought of her. His skill was marvelous, quite refined after plenty of time with one particular partner, and she felt terribly inadequate with her unsure moves. She stopped for a few moments, though gave him a nod to let him know that she wanted him to continue, and just focused on learning his rhythm. She closed her eyes and let the sensations fill her, letting them drive her to the brink, until some kind of instinct urged her to move once more. Now she rolled her hips back against him in time, each impact making her gasp loudly, and she felt a wave of heat as it occurred to her how deep he was, how firmly he was moving, and maybe rough sex was something she could get into...

Then, despite her warning that she didn't like it, he tilted his head and bit at her throat. However, he smoothly switched to sucking on the wound as if that was his purpose all along, and the heat of his mouth on the sensitive skin had her trembling, fingernails clawing at his back for purchase as she felt her edge looming.

It suddenly hit her, and she called out his name as her body convulsed.

“Ooh, fuck...” Bill swore, unprepared for the rhythmic contractions that squeezed so wonderfully around him, though only for a few moments. He soon recovered and continued.

Breathing shakily, Mabel rested her head against one of his arms. “Oh... oh man...” she muttered. She knew he was still going, but she didn't have the energy to respond anymore. All she could do was just enjoy it.

She realized he was moving more slowly now, and one of his arms was sliding under her back, embracing her closer to him. Her skin tingled at the contact, and she sighed quietly in bliss. He was being gentle now, more than she thought possible of his muscular body. It was nice, and she could soon feel heat building back up again. She bucked back against him a few times, enough to climax. Her fingernails bit into his skin hard enough to draw blood, which was exactly what he liked to feel.

With a groan, he had his orgasm, and she almost tensed before remembering that he was wearing a condom.

Panting, Bill just looked at her for a few moments, until she moved her head to look back at him too. Then his hand was at the back of her neck and he was pulling her close for a heated kiss. She did her best to respond, but she wasn't particularly fond of these kinds of kisses. It was too harsh for her liking, especially when he tried to tug on one of her lips with his teeth. So she pulled away from it, blushing when he gave her a knowing smile.

“I'll try again,” he said, and this time, kissed her more sweetly.

That was better. She relaxed into this one, but it was over far too quickly, and he was lowering her down onto the covers so he could withdraw from her. He sat back and removed the condom, tying the end of it shut and looking around for somewhere to put it.

“I keep a small waste basket next to the bed,” Mabel said, pointing it out.

“Ah, thank you.” He leaned over and tossed it in, then looked back at her, crossing his arms and looking very smug. “So. Have fun?”

She laughed. “Yeah. So much fun.”

“Good. I did too, that was interesting. A little different, but not too much.” He laid down next to her, pecking her cheek. “Really, the only hard part was holding back. I prefer a faster pace, but since you don't like that, I didn't do it.”

“You're very considerate.”

“Oh, it was no big deal. Your enjoyment is just as important as mine. I still had fun.” He ran his fingers lightly through her hair, and she leaned into the touch.

“Stay with me?” she asked.

He stared at her. “Of course I'm staying here, you think I'm just gonna up and leave after this?”

“Well... it wouldn't be the first time someone's done that to me.”

“Oh, my bright Shooting Star...” He gave her a sympathetic hug. “Clearly they were assholes, then.”

She laughed. “Clearly.”

“I can't stay here forever, obviously. And I am very fond of Pine Tree... Dipper. He's the one who has really captured my heart. But... I do like you a lot. You're just as intelligent and outgoing as he is, and I find that very intriguing in humans. I could get all philosophical but I don't wanna ruin the mood. I'll just say that it's adorable how much you guys try to get done in such a short amount of time.” He snuggled close to her, and she snuggled right back, enjoying his warmth. He was only a little bit taller than her, but she curled up against him like a puppy anyway.

He was content to hold her, arms around her and a finger tracing little meaningless patterns on her shoulder.

With a pang of longing, she wished he could be hers. But though he was fond of her, his affection belonged to her brother, and she could never have the same relationship with him. And he would never fully commit to her, which was what she really wanted out of a partner. Still, for right now, she could pretend. “This will be our little secret, right?”

He chuckled, and she could feel him draw a heart against her skin. “Of course, Shooting Star. Our secret.”


End file.
